Grinding-bur.



J. H. LETZ.

GRINDING BUR.

APPLICATION FILED MAY 7. Ian.

U ya m, LM I no 6 u. w, 0 um ww i f 4 5 P. Q/r 6 h mY jf m/ n 6 lf m//MMM 4 @FLW/.6 1 f f ED STATES PATENT OFFICE..

JOHN HOLLAND LETZ, F CROWN '.POIN'I, INDIANA, ASSIGNOIR, T0 THE LETZMANU- FACTUBING COMPANY, OF CROWN POINT, INDIANA, A CORPORATION OFINDIANA.

GRINDING-IBUB.

To all whom z't may concern:

Be it known that I, JOHN HOLLAND Ln'rz, a citizen of the United States,and a resident of Crown Point, in the county of Lake and State ofIndiana, have invented certain 'new and useful Improvements in Grindingy Burs, of which the following is a full, clear,

, reference characters are used to designate identical parts in all thefigures, ofwhichf- Figure 1 is a plan view of a portion of a burembodying my invention;

Fig. 2 is a central section on a reduced scale; and FFig.' 3 is asection on the line 3-3 of The base A is an annulus, preferably a metalcasting having the design in cross section as it appears 1n Fig. 2, withthe inclined, depressed annular portion B surrounding the circularfeeding opening, and the pair of customary annular ribs C and D on theback.

The inding ribs are preferably arranged 1n similar sections, as shown,with each section occupying one-sixth of thebur. Three extra-long guideribs E, F and G, substantially parallel to each vother and standing atsubstantially the angle shownV to the central radius of the section,serve to guide the materials out to and distribute them somewhat evenlyover all portions of the section. Each of these ribs, E, F and G,terminates in a short angularly disposed offset E', F and G', whichpreferably extends substantially parallel to the periphery of the bur.Associated with each of these elongated ribs are the shorter parwith theoffsets, not' lettered, but similar to i Speoication of Letters Patent.Patented Oct, 30, 191.7.

Application led May 7, 1917. Serial No. 166,896. l y

the offsets E', F and G, and their inner ends are usually provided withreversely arranged offsets (also notlettered), the oii'- sets of theouter ends of one series of ribs being arranged in staggeredrelationship with the\oifsets of the inner ends of the adjacent serieswhich they closely approach. rIwo additional series of ribs Ha, Hb, I-Icand Ja, J b, J, Jd, J*a and Jf, are provided at the opposite ends ofeach section, and these series extend in the same general direction andhave the same general shape as the other series in the section. All theribs heretofore mentioned extend tothe same height, and have their topsground olf to form shearing edges, as heretofore explained. rious ribsunbroken throughout their lengths, as seen in the fragmentary sectionconstituting the right-hand end of Fig. 1, where the ribs E', Ea', Eb',E", Ed', Ey and I-I, Hb and Hc are seen, I preferably cut out in eachrib two or more recesses K, with said recesses arranged in alinement inthe dierent ribs, so as to furnish a somewhat more direct outlet for somuch of the material as is finely enough ground before it reaches theperiphery.

In addition to the full-height ribs already described, I employ in eachsection plural series of baille ribs L, La, and Lb; M, M, Mb and M; N,N, Nb and Nc; O, Oa, Ob and 0; and P, Pa, Pb and Pc, which, as seen inFig. 3, are slightly lower than the main ribs, and which perform animportant function in preventing the material from moving outward toorapidly, and also, paradoxical as it may seem, in preventing the oilymaterials from clogging in the passages formed by the main ribs. Allaround the'periphery n I employ other lower ribs Q, which serve toprevent the escape of the material from the bur before it is completelyground.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is: 1. A grinding plate having on its surface pluralseriesof long shearing ribs with their ground-ofi' tops in the samehorizontal lane and arranged to form generally paralle andnon-converging passages and all set at a con# siderable angle to radiallines, together with plural series of lower baiile ribs arranged ingenerally radial lines between the shearing ribs.

2, A. grinding plate having on its surface While I might make all theseva'- l plural series of long shearing ribs with their ground-off tops in.the same horizontal plane and arranged to form generally parallel andnon-converging passages and all set at a considerable angle to radiallines, together with plural series of lower baille ribs arranged ingenerally radial lines between the shearing ribs', said shearing ribsbeing provided with cuts therein arranged substantially parallel to theline of the baffle ribs.

3. A grinding plate having on its surface plural series of longitudinalshearing ribs having their ends odset at an angle of substantiallythirty degrees to the line thereof and with their ground-0E tops in thesame horizontal plane and arranged to form generally parallel andnon-converging passages and all set at a considerable angle to radiallines, together with plural series of lower battle ribs arranged ingenerally radial lines between the offset ends of the shearing ribs.

4. A grinding plate having on its surface plural seriesof long shearingribs with their ground-off tops in the saine horizontal plane andarranged to forni vgenerally parallel and non-converging passages andall set at a considerable angle to radial lines,

magere together with plural series of lower bae ribs arranged 1ngenerally radial lines between the shearing ribs, and a line ofcircumferential baiiie ribs, also lower than the shearing ribs.

5. 'A grinding plate havin on its surface plural series of longitudinashearing ribs having their ends ol'set at an angle of substantiallythirty degrees to the line thereof and with their ground-olf tops in thesame horizontal plane and arranged to form generally parallel andnon-converging passages vand all set at a considerable angle to radiallines, and plural series of lower baffle ribs arranged in generallyradial lines between the offset ends of the shearing ribs, the ends ofone series of longitudinal ribs being arranged in staggered relation tothe adjacent ends of the adjacent series of longitudinal ribs.

In witness whereof, I have hereunto set my hand and aliixed my seal,this 26 day of April A. D. 1917.

JOHN HOLLAND LETZ. [1.. s]

Witnesses:

JOHN E. FRAAS, JACOB J. STEEL.

